■French National Instihile. 309 



The mcdtis£e, properly so called, have a gelatinous body 

 nearly of the form of the top of a mushroom, which M. 

 Peroi) calls umbrella, after the example of Spallanzani ; 

 but thcv differ from each other, in as much as some of them 

 have a mouth and others want ii ; some have several mouths, 

 and in others there is a production under the umbrella in 

 the form of a pedicle. 



M. Peron fnnn these characters has formed a tree of di- 

 visions and subdivisions, in which all the medusas in ex- 

 istence must necessarily fall to be classed, and in which he 

 has placed all those with which h-e is acquainted. Faithful 

 and accurate paintings, executtd by his fellow voyager M. 

 Lesueur, explain all that variety of forms and colours so 

 necessary for subjects of natural history. 



To these inquiries into external characters, M. Peron has 

 added some interesting details on the internal structure of 

 these animals, and particularly the genus called r/iizosio- 

 minri. M. Cuvier had so denominated it, because he sup- 

 posed that the filaments attached to its tentacula were so 

 many suckers, and that the nourishment thereby inhaled 

 proceeded to a central cavity, from which it was distributed 

 to the whole body bv an infinite number of vessels arranged 

 very regularly, and midtiplicd particularly in the edf!;esof"the 

 umbrella. The four apertures in the sides of the base of the 

 pedicle appeared to M. Cuvier to be the organs of respiration, 



M. Peron on the contrary, having observed several living 

 rhizostoma, and having seen them take in some small ani- 

 mals by these four apertures, and suck them in towards the 

 four cavities to which they lead, is of opi^iion, that these 

 are four distinct mouths and stomachs, and that the large 

 vascular apparatus, which fills the pedicle and the edges of 

 the umbrella, is with much more probability set apart for the 

 oliice of respiration, as it is almost always filled with air. 



M. Cuvier has this year instructed the class wiih respect 

 to certain species of reptiles, the bones of which have been 

 found buried in the earth. Ail of them liad been regarded 

 as belonging to crocodiles, and even peculiar to a crocodile 

 of the Ganges called the Cavial genus; but there are lizards 

 o( ihc safeguard or tafyinamliis apt-cks, which belong also 

 to the Gavial genus, although they have distinctly marked 

 differencea in their respective characters. 



What is most singular with respect to these fossil bones 

 of reptiles is, that they are found at a much greater depth 

 than those of land animals. 



The cnvMons of Macstritht also contain the bones of a 



jjicat aiiiinal of that family, which some regard as alish and 



U 3 others 



